A motor driving system is incorporated in a vehicle such as an automobile or hybrid vehicle with an electric motor as well as other electric apparatus employing a motor. For such a motor driving system, an angle of rotation detection device detecting the angle of rotation of the motor is employed.
For example, Japanese Patent Laying-Open No. 2009-77481 (Patent Literature 1) teaches the usage of a resolver for a rotation detecting sensor and an R/D (Resolver/Digital) converter that converts the output from the resolver into a digital value to increase or decrease a count value.